Studies on the Synthesis of (2R,4′R,8′R)‐α‐Tocopherol Alternative Syntheses of 2‐Chroman‐acetic Acid Intermediates

As an extension of previous studies on the total synthesis of (2R,4′R,8′R)-α-tocopherol (1) [1] [2], (S)-(−)-2-(6-benzyloxy-2,5,7,8-tetramethylchroman)acetic acid (6), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11. the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.-3-hydroxy-3-methylpent-4-en-l-yl acetate (16) giving rac. ethyl 2-(6-hydroxy-2,5,7,8-tetramethyl-chroman)acetate (12).